Get categories without post

Question

I want to get categories that had NO post. Below is sql for getting category with post..

SELECT terms.term_id,terms.name,COUNT(post.ID) FROM wp_posts as post
JOIN wp_term_relationships as rel ON post.ID = rel.object_ID 
JOIN wp_term_taxonomy as ttax ON rel.term_taxonomy_id = ttax.term_taxonomy_id
JOIN wp_terms as terms ON ttax.term_id = terms.term_id
WHERE ( ttax.taxonomy='category' AND post.post_type='post' AND post.post_status != 'revision') GROUP BY (terms.term_id)    

But how to get catgeory with NO post? Thank you for your help.

Answer 1

Here is how you can list the empty cat's
this way can also refrence each category data like ID, Name etc

$args = array(
    'hide_empty' => 0,
    'pad_counts' => true
);
$categories = get_categories( $args );
foreach($categories as $category) {

    if($category->count == 0) {
        echo $category->name."<br />";
    } else {
        // do nothing
    }

}

Answer 2

You can try this to get empty categories:

$args = array( 'hide_empty' => 1, 'hierarchical' => 0 );

add_filter( 'terms_clauses', 'custom_terms_clauses_wpse_99783' );   
$emptycats = get_terms( 'category', $args );
remove_filter( 'terms_clauses', 'custom_terms_clauses_wpse_99783' );    

where

function custom_terms_clauses_wpse_99783( $clauses ){
    $clauses['where'] = str_replace( 'tt.count > 0', 'tt.count = 0', $clauses['where'] );
    return $clauses;
}

The reason for these input arguments is to target:

    if ( $hide_empty && !$hierarchical )
            $where .= ' AND tt.count > 0';

in the function definition of get_terms, so we can do the replace.